A laser device having a hollow cathode has many advantageous characteristics compared to one utilizing a small capillary discharge tube. The hollow cathode laser can be fabricated simply, resulting in a low-cost laser device. It lends itself to the use of ceramic and metal parts which can be brazed together to form a rugged tube structure. The design has a compactness, which is not often obtained with other types of lasers and it can be provided with a short overall length, as compared to most laser devices. A hollow cathode metal vapor laser can be operated at low voltages, around 300 volts, thus requiring only a simple power supply for its operation. The hollow cathode laser provides, in some applications, light emission of wavelengths not found in a capillary laser tube using the same lasing materials. Since the hollow cathode laser operates with a positive voltage-to-current characteristic, modulation of the laser output can be accomplished simply by varying the discharge current.
However, it is well recognized that hollow cathode lasers have severe material problems. For example, the cathode electrode of a laser using a metal vapor undergoes an intense ion bombardment, which causes a rapid sputtering of the cathode surface metal. After only a few hours of operation, the sputtered material covers insulating surfaces and obstructs the optical paths through the laser bore. The sputtering action also may cause the cathode to disintegrate and loss in the gaseous filling.